A video RAM (VRAM), sometimes called a dual-port RAM, is a DRAM (Dynamic Random Access Memory) having a serial I/O port coupled to a serial access memory (SAM). The SAM permits a block of stored data to be rapidly accessed, while the normal access function of the DRAM is also occurring. The information in the SAM is normally obtained from, or input into, a primary memory on the VRAM. The primary memory may be configured as a DRAM array and is accessed according to DRAM protocols.
Information may be written into the VRAM at DRAM address speeds and output through the serial access port, or vice versa. This is convenient for video applications because some address sequences, such as pixels in a raster scan, are predetermined. An object of the present invention is to increase the speed at which data is output to the serial port in a VRAM.